Ensitrelvir (code name S-217622, brand name Xocova), is a new inhibitor of the SARS-CoV-2 major protease (Mpro), also known as 3C-like protease, has been shown to reduce the viral load and help alleviate the severity of SARS-CoV-2 in infected hamsters. In cells, low nanomolar to sub-micromolar doses of Ensitrelvir suppress viral growth. In hamsters, oral treatment of Ensitrelvir showed excellent pharmacokinetic qualities and hastened recovery from acute SARS-CoV-2 infection.

Ensitrelvir also demonstrated antiviral effectiveness against SARS-CoV-2 variants of concern (VOCs), such as the highly pathogenic Delta variant and the newly discovered Omicron variant. Overall, these findings show that Ensitrelvir, which is an antiviral drug that is currently being tested in Phase II/III clinical trials, has impressive antiviral efficiency and effectiveness against SARS-CoV-2 and could be a viable oral treatment option for COVID-19.

The mechanism of action of Ensitrelvir

Like Paxlovid, Ensitrelvir also targets the 3CL protease (3CLpro). These two oral drugs are designed to block the activity of the SARS-CoV-2-3CL protease, thereby blocking the replication of the novel coronavirus. Now, The Ensitrelvir’s Phase III clinical trials is completed. It became the first Japanese domestic pill to treat COVID-19 and the third to be regulatorally approved in February 2022 in Japan.

The treatment effects of Ensitrelvir

Results of a clinical trial of Shionogi's oral drug Ensitrelvir in 428 patients over the age of 12 with mild and moderate symptoms showed that the novel coronavirus was undetectable in 80% of patients on day 4 of three days of oral administration. On the 6th day after taking it for 5 days, the new coronavirus in 100% of the people has completely disappeared.

The clinical trial results also showed that after taking Ensiprevir, symptoms such as runny nose, nasal congestion, sore throat, cough, and dyspnea were greatly improved, with minimal side effects. And it has a significant inhibitory effect on the proliferation of the novel coronavirus strain of Omicron. The oral drug Ensitrelvir developed by Shionogi is a pill. Once approved by the Japanese government, it is expected to become an over-the-counter medicine like cold medicine and a powerful weapon against the COVID-19 epidemic.

The applicable groups of Ensitrelvir

Paxlovid is mainly administered in people over the age of 12 with mild symptom and tend to become severe. But for Ensitrelvir, people over the age of 12 who have been diagnosed as positive can take it, regardless of whether there is a tendency for exacerbation, whether they have symptoms or not. It has a wider range of treatments than Paxlovid.

For Ensitrelvir, regardless of whether there is a tendency to become severe or not, can be taken by people over 12 years old who are diagnosed as positive, regardless of whether they have symptoms or not. It has a wider range of treatments than Paxlovid.

Huateng Pharma is a global provider in contract development and manufacturing for intermediates. We can manufacture, scale-up and supply high-quality intermediates and APIs from our China facility. We can provide custom synthesis from R&D to commercial production of Ensitrelvir intermediates as following.


Ensitrelvir (S-217622) Intermediates:

CAS NO.:1360105-53-8 3-Tert-butyl-6-(ethylthio)-1,3,5-triazine-2,4(1H,3H)-dione
CAS NO.:1893125-36-4 6-Chloro-2-methyl-2H-indazol-5-amine
CAS NO.:135206-76-7 3-(Chloromethyl)-1-methyl-1H-1,2,4-triazole
CAS NO.:157911-56-3 2,4,5-Trifluorobenzyl bromide
CAS NO.:76-05-1 Trifluoroacetic acid